LM7 5.3 with small cam.


Someone please explain this startup idle. It starts fine and climbs to 1500 or so. After a second or two, it climbs farther to over 2000, why? and then slowly lowers to its resting idle. This seems like a vacuum leak to me but I have smoke tested, brake cleaner tested. Changed intakes, changed TBs and got a new IAC .

This is a cold start but it does is while warm as well although jumps to 3000 before returning to normal idle. The only other thing I can see it a tune issue. Other than this start up idle, it runs fine.

 

How clean is the throttle body?

 

Sounds like a tune issue. I don't remember where in HP Tuners you adjust that but if you have a cam one thing you adjust is base running airflow.

 

post a tune and a log.
Make sure you log STIT, LTIT, startup airflow, IAC desired and actual posistion.